As is generally known, an automotive vehicle, which uses an internal combustion engine, is equipped with an evaporative fuel processing apparatus mainly constructed by a canister for suppressing evaporative fuel generated within a fuel tank from being discharged into the atmosphere. The canister has a canister case charged with an adsorption material such as activated charcoal or carbon. The canister is configured to temporarily adsorb and trap evaporative fuel generated from within the fuel tank by the adsorption material in a vehicle stopped state where the internal combustion engine is stopped, and allow fuel components from the adsorption material to be desorbed by atmospheric air introduced through a drain port (also called “atmospheric port”) during operation of the engine, and purge the air containing the fuel vapor desorbed from the adsorption material (the activated carbon) into the intake system of the engine.
One such canister has been disclosed in patent document 1 (JP2014-234717 corresponding to United States patent application publication No. US 2014/0352541 A1). The canister, as disclosed in the patent document 1, is equipped with a laterally-curved purge port configured to extend from the center position of one axial end of the cylindrical case and located on the center line (the axis) of the case, and a charge port connected to a sidewall surface of the one axial end of the case. Also provided at the one axial end of the case is a flange for partitioning a part of an adsorption material chamber. The flange is formed with a cylindrical portion protruding toward an adsorption material chamber. The flange is also formed with a plurality of circumferentially equidistant-spaced orifices, through which the adsorption material chamber and a diffusion chamber (this diffusion chamber is configured to communicate with the charge port) are communicated with each other. Evaporative fuel (charge gas) is introduced from the charge port into the diffusion chamber, and then guided into the adsorption material chamber by way of the plurality of orifices. The previously-noted cylindrical portion is provided to prevent the charge gas containing fuel components at high concentration from flowing directly toward the purge port without being adsorbed or trapped by the adsorption material.